Aqueous highly alkaline hair relaxing or straightening compositions are known in the art. These compositions usually have a highly alkaline pH of about 12 to about 14 due to the presence of an alkaline material, such as water-soluble alkali or alkaline earth hydroxide or an organic chemical base such as guanidine, guanidine hydroxide or quaternary ammonium hydroxide.
Modern highly alkaline hair relaxers are preferably of the type commonly called "no-base" hair relaxers. The term "no-base" means that the scalp need not be coated with a protective oleaginous base such as petrolatum, mineral oil and lanolin, before applying the highly alkaline hair relaxer.
One type of no-base hair relaxer formulation contains as the active hair straightening agent an alkali metal hydroxide, typically a caustic base, such as sodium hydroxide or potassium hydroxide. When a relatively low active level of about 1.5 to about 2.5 weight percent of caustic base is used, the protective base is applied only to the hairline to protect the skin around the forehead, ears and neckline. Such no-base formulations preferably have some of the protective oleaginous material emulsified in an aqueous composition, and are supplied in a "single product" kit.
A preferred and more recently developed type of no-base hair relaxer formulation is commonly called a "no-lye" hair relaxer. With a no-base, no-lye relaxer, a protective base need not be applied to the scalp and may not need to be applied to the hairline. The term "no-lye" means that the active hair straightening agent is an organic chemical base instead of caustic base. In commercial practice, the relatively strong organic chemical base, guanidine is usually present in the form of guanidine hydroxide. However, guanidine hydroxide is not generally stable for long periods in aqueous solutions. Consequently, it must be prepared fresh just before using.
Guanidine hydroxide is generally prepared by reacting an inorganic chemical base such as an alkaline earth hydroxide with an aqueous solution of a salt of the strong organic chemical base guanidine where the anion of this salt is capable of being precipitated by the cation of the alkaline earth hydroxide. In commercially available products of this type, the guanidine hydroxide is generally prepared using guanidine carbonate and calcium hydroxide.
When such a no-lye hair relaxer is commercially used, the product is supplied as a two-part kit. One part contains the guanidine carbonate in substantially liquid form and is commonly called the "activator." The other part contains relatively high amounts of about 4 to about 7 percent calcium hydroxide emulsified in a cosmetic cream base. Prior to using, the consumer or beautician mixes the cream and activator portions of the kit together. The resulting no-lye hair relaxer is then relatively promptly (preferably within 24 hours) applied to the hair.
For convenience, the term "no-lye cream base" as used herein means the cosmetic cream base portion of the foregoing kit containing alkaline earth hydroxide. The term "activator" means the substantially liquid portion of the kit containing the organic chemical base, and the "no-lye hair relaxer" means the resulting admixture of the foregoing no-lye cream base and activator. The term "no-base hair relaxer cream," refers generally to a highly alkaline hair straightening product whether supplied as a single product or as a two-product kit.
Some great strides have been made in formulating highly alkaline no-base hair relaxer compositions, such that proper hair shaft penetration by the active alkaline material is achieved along with minimal scalp injury to thereby improve safety. Also by the incorporation of conditioning agents, the straightened hair has a better feel after such a treatment. However, highly alkaline emulsion products are difficult to compound, require much care during preparation on a commercial scale, and separate or de-emulsify relatively quickly on ageing thereby limiting their commercially useful lifetime.
Most no-base cream products are preferably aqueous emulsions in which water is the continuous phase, i.e., oil-in-water emulsions, because they are easier to rinse from the hair. Instability or de-emulsification therefore results in a destabilized cream product having two distinctly visible phases.
While such destabilized products may be used, they must be remixed before using in an attempt to assure the user that the active ingredients are at the proper levels in the portion being used. However, such mixing, even though done thoroughly by hand, does not, in fact, give the user consistent results with such products. Improper mixing can also cause skin irritation or result in increased hair breakage. Product destabilization and resulting consumer dissatisfaction are among the chief complaints in the industry.
The term "phase-stable" cream refers to an emulsion composition that shows substantially no visible separation into distinct phases on ageing. Thus, phase stability refers to physical stability and is not intended to refer to the chemical stability of the non-alkaline individual ingredients against decomposition by or interaction with the alkaline material under highly alkaline conditions over a relatively long lifetime.
Problems of instability are also caused by the presence of relatively high amounts of water-insoluble oleaginous ingredients that must be co-emulsified with the alkaline material. Oleaginous materials, such as petrolatum and lanolin are desirable in no-lye cosmetic cream bases to maintain the benefits of a no-base procedure. But their water-insoluble character greatly decreases the chances of successfully formulating a phase-stable cream. These problems are magnified when a formula is scaled up for the production of commercial quantities.
Part of the foregoing problems were overcome in U.S. Pat. No. 4,390,033 ('033) and U.S. Pat. No. 4,237,910 ('910), both to our assignee, by the use of certain lipophilic organically-modified hectorite clay gellants. The disclosures of the '033 and '910 patents are incorporated herein by reference. Those clay gellants were disclosed for stabilizing highly alkaline no-base hair relaxer compositions containing relatively high amounts of oleaginous material against phase separation. Commercial hair relaxer products embodying the principles disclosed in these patents have been marketed.
However, compounding a phase-stable cream, even with the above disclosed hectorite clay gellant, requires considerable care to substantially uniformly disperse the disclosed hectorite clay gellant. In addition, relatively high amounts (about 8 to about 1 weight percent) of the hectorite clay gellant are generally required to achieve a relatively stiff viscous cream. For example, the '033 and '910 patents disclose that at below about 2 weight percent of the hectorite clay gellant, little phase stability improvement was noted and the resulting creams were relatively soft. Thus, while generally elegant relatively stiff viscous creams can be obtained by practicing the emulsion stabilizing principles taught in the '033 and '910 patents, the products are relatively costly to manufacture commercially from the standpoints of costs for labor, materials and energy.
No-base hair relaxers are desirably formulated as emulsified viscous creams so that once applied to the user's hair, they will not drip onto the skin or into the eyes of the person receiving a hair straightening procedure. The cosmetic cream base portion of a no-lye hair relaxer must also mix easily with the activator solution without thinning to a soft runny cream. Additionally, an ideal no-base hair relaxer cream must be easy to remove from the hair at the end of the straightening or relaxer procedure.
The present invention provides such a phase stable cosmetic cream base for use in no-base hair relaxer cream in which many of the above drawbacks in cost are substantially lessened or obviated while retaining the ease of use benefits.